Volume 29, Number 7—July 2023
Research Letter
Low Susceptibility of Pigs against Experimental Infection with HPAI Virus H5N1 Clade 2.3.4.4b
, Ronja Piesche, Julia Sehl-Ewert, Christian Grund, Anne Pohlmann, Martin Beer, and Timm Harder
Table
Detection of seroconversion and of influenza A viral loads in tissues and nasal swabs of experimentally infected pigs exposed by intranasal or alimentary inoculation with HPAI virus H5N1 clade 2.3.4.4b virus*
| Infection route |
Day postinoculation |
Animal ID |
GEq, by qRT-PCR |
NP-ELISA Seroconversion |
||||||
| Nasal swabs† |
Conchae nasalis |
Trachea |
Lung |
Ileocaecal tonsil |
Colon |
Brain |
||||
| Intranasal |
4 | 1 | 30 | – | – | – | – | – | – | – |
| 4 | 2 | 150 | – | – | – | – | – | – | – | |
| 14 | 3 | 30 | 10 | – | – | – | – | – | – | |
| 14 | 4 | 10 | 60 | – | 10 | 170 | 200 | 350 | + | |
| 14 |
Sentinel |
– |
– |
– |
– |
– |
– |
– |
– |
|
| Alimentary |
4 | 1 | – | – | 5 | – | – | – | – | – |
| 4 | 2 | 30 | – | – | – | – | – | – | – | |
| 14 | 3 | 20 | – | – | – | – | – | – | – | |
| 14 | 4 | 140 | – | – | – | – | – | – | – | |
| 14 |
Sentinel |
– |
– |
– |
10 |
– |
– |
– |
– |
|
| Intranasal positive control‡ | 4 | 1 | 300,000 | 10,000 | 860,000 | 5,400 | NA | NA | NA | – |
| 4 | 2 | 83,000 | 35,000 | 56,000 | 1,500 | NA | NA | NA | – | |
| 4 | 3 | 750,000 | 4,300 | 1,600,000 | 1,500 | NA | NA | NA | – | |
| 4 | 4 | 710,000 | 29,000 | 520,000 | 1,100 | NA | NA | NA | – | |
*Shown are only tissues for which >1 animal has tested positive. GEq, genome copy equivalents per 0.1 mL calculated on the basis of qRT-PCR quantification of cycle values; HPAIV, highly pathogenic avian influenza; ID, identification; NA, not applicable; qRT-PCR, quantitative reverse transcription PCR; +, positive; –, negative. †Nasal swabs positive at day 2 postinfection for the intranasal group and day 4 postinfection for the alimentary group. ‡Four pigs, infected with the same device and dose of a swine-adapted influenza A virus strain (subtype H1avN1, clade 1C2.1) of a former study are included for comparison (9). Pigs were sacrificed at day 4 post infection when no seroconversion was to be expected; gastrointestinal tissues and brain were not examined.
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